This gets a lot less rarefied and more obviously practical if you think of it as applying to specific diatonic instruments, like the melodeon, diatonic autoharp or mouth organ.

e.g. E dorian uses the D row on your melodeon, tonic chord is E minor, IV is A major, V is B minor. If your instrument can't produce a D major scale you can't play the tune and if you can't produce those chords you probably can't harmonize it. It's got nothing to do with intonation systems and less to do with church music.

See the tutorial on my website for instrumental applications of gapped scales.